An acoustic logging tool may include one or more acoustic receivers. Acoustic signals may be transmitted by a variety of acoustic sources and received at the receivers as the tool passes through a borehole. Thus, the acoustic signal from a particular source may travel through the formation adjacent the borehole to the receiver array, such that arrival times and other characteristics of the receiver response may be recorded. Received signals may include compressional waves (P-waves), shear waves (S-waves), and Stoneley waves. Received signal data may be processed to determine signal travel distance and formation characteristics, including slowness (the inverse of acoustic speed), from which pore pressure, porosity, and other formation property determinations can be made.
Traditional acoustic tools may detect acoustic signal travel times based on a selected trigger threshold. However, the usefulness of measurements obtained may be reduced due to the presence of various noise sources. Low thresholds may cause false trigger indications, and high thresholds may prevent detection of desired signals.